Sensitized photographic emulsions



April ll, 1939. D KENDALL Y 2,153,928

SENS ITIZED PHOTOGRAPHIC EMULS IONS Filed May l, 1936 UN TEEATED SILVER CHLOE/9E 'MLS//V Patented pr. l1, 1939 John David Kendall, Ilford. England. assigner to Ilford Limited, Ilford, Essex,

company EnllsnILnBrltilh Application May l, 1936. Serial No. '17,441

In Great Britain May 8. 1985 v 12 Claims.

This invention consists in improvements in or relating to sensitizing photographic silver yhalid emulsions.

The colour senstive range of photographic silver halide emulsions has been extended by incorporating in the emulsion many different compounds, including dyestuffs of the cyanine and of the pinaflavol classes. The cyanine dyestuii's consist of a, heterocyclic nitrogen nucleus containing a quinquivalent nitrogen atom, such as that in a quaternary salt, which is linked to a heterocyclic nitrogen nucleus containing a trivalent nitrogen atom by amethine or polymethine chain. The pinaflavol dyestuffs consist of a heterocyclic nucleus containing a quinquivalent nitrogen atom which is linked to a trivalent nitrogen atom by a conjugate chain of carbon atoms part of which is included in a homocyclic ring.

Both these types of compound have 'been employed extensively for sensitlzing photographic silver halide emulsions, and in both classes an essential feature is the presence of a quaternary nitrogen atom linked by a completely conjugate chain to a trivalent nitrogen atom. It has generally been supposed that it is the presence of this system which imparts the sensitizing action to the compounds and that compounds which do not contain the system would not possess sensitizing properties.

I have now found that the above-mentioned system is not essential for a. compound to have sensitizing properties, and that compounds containing no quinquivalent nitrogen atom, but coni taining two trivalent nitrogen atoms linked together by a completely conjugate chain of an odd number of carbon atoms possess strong sensitizing properties.

According to the present invention therefore a method of sensitizing photographic silver halide emulsions comprises incorporating in the emulsion an organic nitrogen compound containing no quinquivalent nitrogen atom but containing two trivalent nitrogen atoms linked together by a completely conjugate chain of an odd number of carbon atoms linked by alternate double and single bonds.

Although a completely conjugate chain of carbon atoms is referred to above, it is to be understood that compounds containing a singlev methine group connecting two trivalent atoms, and linked to one by a single bond and to the other by a double bond, act es sensitizersand are included within the method of the present invention. It is found, however, that compounds which are visibly coloured, i.'e., which absorb light falling within the visible spectrum or in the near ultra violet, e. g.` about 3500 are more effective as sensitizers than the uncoloured orfaintly coloured compounds which absorb the radiations in the shorter ultra violet wave lengths. vThe colour o (ci. ss-'n the compounds which are to be employed in accordance with the present invention is dependent to a certain extent on the number of carbon atoms in the chain linking the two ternary nitrogen atoms and it appears that the longer the chain the more the absorption and sensitizing range is displaced towards the red or longer wave lengths so that generally speaking compounds containing a number of carbon atoms in the chain are preferred. It-is also found that the nature oi the systems or nuclei containing the nil trogen atoms seems to iniluence the colour sensitizing effect of the compound, for example the inclusion of one or both of the nitrogen atoms in heterocyclic nuclei tends to displace the absorption band towards the red or longer wave lengths and to give a more extended colour sensitivity efi'ect.

Investigations have shown that the best sensitizing eiects are obtained when compounds are used in which two nitrogen atoms are contained in diierent heterocyclic nuclei and are linked by a completely conjugate chain of at least three carbon atoms, for example the bases corresponding to the cyanine and carbocyanine dyes and other dyes of the same or analogous series.

The cyanine bases may be obtained, for example by condensing a heterocy'clic nitrogen base having a reactive methyl group in the a or y position to the nitrogen atom with a quaternary salt of a heterocyclic nitrogen compound having a reactive thioether or selenoether grouping (including the reactive grouping of an alkyl salt of an N-alkyl thione or selenone) or an amino-vinyl or substituted amino-vinyl grouping (including an arylamino, acylamino. or acylarylamino-vinyl grouping) in the a or y position to the nitrogen atom, or with a condensation product having the general formula:

where D=the residue of the heterocyclic system, R=an alkyl, aryl or aralkyl group, X= an acidic group. Y=arylamino group and n=a positive integer, such as is obtained by condensing a compound of the general formula (where Z=a substituted amino group, and Y andv n as above) with a quarternary salt of a heterocyclic nitrogen base having a reactive methyl group in the a or 'y position to the nitrogen atom.

Generally speaking the carbon atoms forming the completely conjugate chain may be linked to hydrogen atoms or to other neutral monovalent atoms or groups e. g.. albi, aryl or aralkyl groups or halogen atoms and they may form parts of cyclic nuclei. and provided there is an odd number oi carbon atoms in the chain. that is 1, 3, 5', 7, etc. in all cases the compounds possess the desired sensitizing action.

In carrying out the present invention in practice one of more or the compounds to be used in accordance with the present invention may be incorporated in the photographic silver halide emulsion before it is coated on a support, or alternatively the support (e. g. a nlm or a plate) coated with the emulsion may be bathed in a solution oi' one or more oi the compounds. 'Ihe actual quantity of the compound incorporated in the emulsion will vary to acertain extent with the individual compounds, and with the ultimate effect which it is desired to obtain. As an indication of the order of the quantities employed cc. of a one in one thousand solution of the dye may be incorporated in six and a half litres o! emulsion equivalent to about two hundred and iiity grammes of silver nitrate, or the coated support may be bathed in a one in one thousand solution of the compound. The strength of the solution may vary according to the dye used and may be as low as one in ten thonsand.

'I'he difference between the edects produced on photographic emulsions by the cyanine and pinailavol bases employed according to the present invention and the eiects produced by the corresponding salts (e. g. cyanine and pinailavol dyes) are shown in the following examples and illustrated in the accompanying drawing:

(A) 1-p-dimethulamno-sturul-benzthiazole B\ N/on N/ erken-- \CH extends the sensitivity oi photographic silver chloride emulsion to about a 5600 A., with a maximum eiect at about A 4800 The corresponding Quaternary salt 1pdimeth ylaminostyryl benzthiazole ethiodide (B) 2-methuldihydrobenzthazolyldene quina!- dine @xsf/O N/ `N Cgi:

is a powerful sensitiser and sensitises a silver chioride emulsion to about i sooo A. with a maximum at about i szoo A.

ananas The corresponding salt 2.2dimethylthioquino cyanine iodide CH: CH:

is a moderate sensitiser and extends the sensitivity of the same silver chloride emulsion as used above over a band from about A4200 to x 5500 with a strong maximum at about i 5350 'I'he sensitising eiects oi' these compounds are shown in Figure 1I, the top curve of which shows the spectrogram ot a silver chloride emulsion treated with the base and the middle curve of which shows the spectrogram of the same emulsion treated with the salt. 'Ihe bottom curve shows the spectrogram oi' the untreated emulsion.

(C) 1 :3 :3-trimethulindclyidne-2 :1 ':eth1llidene quinaldine CH3 CHI is a powerful sensitiser and extends the sensitivity of the normal silver iodo bromide emulsion to about x 7000 with a maximum at about i cyanine iodide CH CH is a moderate sensitiser and extends the sensitivity oi' the same silver iodo-bromide emulsion to about A 6700 with an indeterminate maximum at about i 6200 Their sensitising effects are shown in Figure III the top curve of which shows the spectrogram of a silver iodobromide emulsion treated with the base, the middle curve of which shows the spectrogram of the same emulsion treated with the salt, and which shows the spectrogram oi the untreated emulsion.

Other examples of pinalavol and cyanine bases which may be used in accordance with the present invention are as follows: y

(l) Z-paradimethylamw iyryl-quinoline CC CH Nyc CH extends the sensitivity of a silver chloride photographic emulsion to about A 5800 with a maxim'um effect at about A 4800 (2) 4-p-dmethylaminostyrylquinoline is a powerful sensitiser and extends the sensitivity of a silver chloride emulsion to approximately i( 5600 A. with a mammum to about i sooo A.

(3) 1-p-dimethylaminostyryl-4-dimethylaminobenzthiazole is a powerful sensitiser and increases the sensitivity of a silver chloride emulsion to approximately i 5600 5600 A. with maxima at about A 4800 A. and A (7) N-ethyldhydrobenzthazolulidene quina!- dine is a powerful sensitiser and extends the sensitivity of a silver bromide emulsion to about A 5700 A. and A 5800 A. with a maximum oi about A 5100 A.

(8) 1 -methyldihydroquinolyldene- (2 :2' quinaldne is a sensitiser and extends the sensitivity of a silver chloride emulsion to about A 5800 with maxima at about A 5200 A. aud A 5500 A.

(9) N-methyldihydrobenzoazolvlidene quinaldine is a sensitiser and increases the sensitivity of a silver chloride emulsion to about A 5000-.

with two maxima at about A 4400 A. and A 4800 A.

(10)' N-methyldihydrobenathiazolylidene lepidine is a sensitiser and sensitises silver chloride emulsion over a band from about A 4300 to A 5400 A. with a maximum at about A 5200 A.

(11) N methyldihydrobenzthiazolylidene-ii methylquinaldine is a powerful sensitiser and extends the sensitivity of a silver chloride emulsion to about A 5500 A. with maxima at about A 4700 A. and A 5100 A.

(12) N-memyz-4-5-dimethoxudfnydrobenatmazolyldene quinaldine is a sensitiser and extends the sensitivity of silver chloride emulsions to about A 5800 A. with maxima at A 5000 A. and A 5500 (13) N-methyl-4:5-dinwtnoxydhydrobenzselenazolylidene quinaldine is a sensitiser and extends the sensitivity of a silver chloride emulsion to about A 5400 with an indeterminate maximum at about A4750 A.

is a sensitiser and extends the sensitivity of a photographic silver chloride emulsion to A 5500 with two iudetemunate maxima at A 4500 A. and A 4800 A.

I claim:

1. A sensitized photographic silver halide emulsion in which is incorporated p-dimethylamino styryl benzthiazole.

2. A sensitized photographic silver halide emulsion in which is incorporated 2-methyl-dihydro- 'benz'thiazolylidene quinaldine.

.3. A sensitized photographic silver halide emulsion in which is incorporated 1:3:3-trimethyl indo1yidine-2' 1'ethylidene quinaldine.

4. A photographic silver halide emulsion containing in sensltizing amounts a compound selected from the group consisting of compounds yofthe general formula:

and compounds of the general formula:

cox ox A1 kN F"- I).- wherein D represents the atoms necessary to complete a heterocyclic nitrogen molecule; R represents a hydrocarbon radical; A is a radical selected from the group consisting of heterocyclic nitrogen bases linked to the open chain in a position of the group consisting of a and y to the ring nitrogen atom; A ls an aminoaryl radical, n is a positive integer and the Xs are members of the group consisting of hydrogen, alkyl. aryl, aralkyl and halogen groups, and Y is a positive integer less than 3; having a conjugated chain with an odd number of carbon atoms between the two nitrogen atoms.

5. -A photographic silver halide emulsion containing in sensitizing amounts a compound selected from the group consisting of compounds of the general formula:

and compounds of the general formula:

` C-(cxFoxm-A.

wherein D represents the atoms necessary to complete a heterocycllc nitrogen nucleus of the type contained in cyanine dyes; R represents a hydrocarbon radical: A is a radical selected from the group consisting of heterocyclic nitrogen bases linked to the open chain in a position of the group consisting of a and 'y to the nitrogen atom; A is an aminoaryl radical; n is a positive integer less than 3 and the Xs are members of the group consisting of hydrogen, alkyl, aryl, aralkyl, and halogen groups', having a conjugated chain with an odd number of carbon atoms between the two nitrogen atoms.

6. A photographic silver halide emulsion containing in sensitlzlng amounts a compound selected from the group consisting of compounds of the general formula:

and compounds of the general formula-z wherein D represents the atoms necessary to complete a heterocyclic nitrogen nucleus oi.' the type contained in cyanine dyes; the Rs represent a1- kyl radicals; A is a radical selected from the group consisting of heterocyclic nitrogen bases linked to the open chain in a position o! the group consisting of a and 'y to the nitrogen atom n is a positive integer less than 3 and the Xs are members of the group consisting of hydrogen, alkyl, aryl, aralkyl and halogen groups; having a. conjugate chain with an odd number of carbon atoms between the two nitrogen atoms.

7. A photographic silver halide emulsion containing in sensitizing amounts a compound of the N/c-c argom@ /R.

wherein the Rs are alkyl groups; and the Xs are members of the group consisting of hydrogen, a1- kyl. aryl, aralkyl, and halogen groups, and havananas ing a conjugated chain with an odd number of carbon atoms between the two nitrogen atoms.

9. A photographic silver halide emulsion containing in sensitizing amounts a compound of the formula:

wherein the R's are hydrocarbon groups; .n is a positive integer less than 3; and the Xs are members of the group consisting of hydrogen, allcvl, aryl, aralkyl, and halogen groups.

12. A photographic silver halide emulsion containing ln sensitizing amounts a compound of the formula set forth in claim l1, wherein the hydrocarbon radicals are alkyl groups.

JOHN DAVID KENDALL. 

